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Network Working Group                                       G. VaudreuilRequest for Comments: 3803                           Lucent TechnologiesObsoletes:2424                                               G. ParsonsCategory: Standards Track                                Nortel Networks                                                               June 2004Content Duration MIME Header DefinitionStatus of this Memo   This document specifies an Internet standards track protocol for the   Internet community, and requests discussion and suggestions for   improvements.  Please refer to the current edition of the "Internet   Official Protocol Standards" (STD 1) for the standardization state   and status of this protocol.  Distribution of this memo is unlimited.Copyright Notice   Copyright (C) The Internet Society (2004).Abstract   This document describes the MIME header Content-Duration that is   intended for use with any time varying media content (typically   audio/* or video/*).1.  Introduction   This document describes the MIME header Content-Duration that is   intended for use with any time varying media content (typically   audio/* or video/*).  The length of time is represented in seconds   without any units indication.  This document obsoletesRFC 2424.   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this   document are to be interpreted as described inRFC 2119 [REQ].2.  Content-Duration Header Field   Time varying media contents, for example, a spoken voice message or a   video clip, have an inherent time duration.  Many audio and video   encodings may include their duration as header information or may   allow accurate calculation based on the byte length of the data.   However, it may be useful to present the time duration of the content   in a MIME header to allow its simple determination without dealing   with the actual content.Vaudreuil, et al.           Standards Track                     [Page 1]

RFC 3803        Content Duration MIME Header Definition        June 20042.1.  Syntax   The Content-Duration field's value is a single number specifying the   time duration in seconds of the content.  Formally:   duration := "Content-Duration" ":" 1*10DIGIT   Note that practically (though highly unlikely in MIME media), the   upper bound on the numerical value of the time duration is (2^^31 -1)   or 2147483647.2.2.  Semantics   This field represents the time duration of the associated time   varying media content.  The time duration is noted in seconds with no   units tag. The time value should be exact, however the exact value of   the time duration cannot be known without opening the content and   playing it.  If an exact value must be known, then the latter method   should be used. This mechanism simply allows placing a sender   determined time duration value in the header for easy access.   Though there are several ways to present this duration to the   recipient (e.g., with the inbox headers, when audio attachment   opened), the actual use of this field on reception is a local   implementation issue.2.3.  Example   In this example the content duration represents 33 seconds:         Content-Duration: 333.  VPIM Usage   The Content-Duration header field for the audio/32KADPCM sub-type is   a useful component of the VPIM specification [VPIM2].  All VPIM   Messages MUST contain this sub-type to carry the audio of a voice   message.  It may be useful in some instances (e.g., viewing on a   simple MIME or non-MIME desktop) to have the time duration of the   voice message available without having to open the audio content.Vaudreuil, et al.           Standards Track                     [Page 2]

RFC 3803        Content Duration MIME Header Definition        June 20044.  Security Considerations   This definition introduces the option of explicitly identifying the   time duration of an audio/* or video/* content outside of the binary   data that forms the content.  In some environments (though likely not   the majority), the identification of the actual time duration in a   header field may be a security issue and as a result should not be   noted. Reliance on the time indicated in this header field cannot be   trusted for the purposes of determining the exact size of the data.   The exact length of the data must be determined by examining the data   itself.5.  References5.1.  Normative References   [MIME2]   Gellens, R., "The Text/Plain Format Parameter",RFC 2646,             August 1999.   [VPIM2R2] Vaudreuil, G., and G. Parsons, "Voice Profile for Internet             Mail - version 2 (VPIMv2)",RFC 3801, June 2004.   [REQ]     Bradner, S., "Key words for use in RFCs to Indicate             Requirement Levels",BCP 14,RFC 2119, March 1997.5.2.  Informative References   [DUR]     Parsons, G. and G. Vaudreuil, "Content Duration MIME Header             Definition",RFC 2424, September 1998.   [VPIM2]   Vaudreuil, G. and G. Parsons, "Voice Profile for Internet             Mail - version 2",RFC 2421, September 1998.6.  Changes fromRFC 2424   Only editorial and boilerplate changes fromRFC 2424 have been made   to this document.Vaudreuil, et al.           Standards Track                     [Page 3]

RFC 3803        Content Duration MIME Header Definition        June 20047.  Authors' Addresses   Gregory M. Vaudreuil   Lucent Technologies   7291 Williamson Rd   Dallas, TX  75214   United States   EMail: gregv@ieee.org   Glenn W. Parsons   Nortel Networks   P.O. Box 3511, Station C   Ottawa, ON  K1Y 4H7   Canada   Phone: +1-613-763-7582   Fax:   +1-613-763-2697   EMail: gparsons@nortelnetworks.comVaudreuil, et al.           Standards Track                     [Page 4]

RFC 3803        Content Duration MIME Header Definition        June 20048.  Full Copyright Statement   Copyright (C) The Internet Society (2004).  This document is subject   to the rights, licenses and restrictions contained inBCP 78, and   except as set forth therein, the authors retain all their rights.   This document and the information contained herein are provided on an   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET   ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,   INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE   INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.Intellectual Property   The IETF takes no position regarding the validity or scope of any   Intellectual Property Rights or other rights that might be claimed to   pertain to the implementation or use of the technology described in   this document or the extent to which any license under such rights   might or might not be available; nor does it represent that it has   made any independent effort to identify any such rights.  Information   on the procedures with respect to rights in RFC documents can be   found inBCP 78 andBCP 79.   Copies of IPR disclosures made to the IETF Secretariat and any   assurances of licenses to be made available, or the result of an   attempt made to obtain a general license or permission for the use of   such proprietary rights by implementers or users of this   specification can be obtained from the IETF on-line IPR repository athttp://www.ietf.org/ipr.   The IETF invites any interested party to bring to its attention any   copyrights, patents or patent applications, or other proprietary   rights that may cover technology that may be required to implement   this standard.  Please address the information to the IETF at ietf-   ipr@ietf.org.Acknowledgement   Funding for the RFC Editor function is currently provided by the   Internet Society.Vaudreuil, et al.           Standards Track                     [Page 5]